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Title: Identification and characterization of nucleolin as a c-myc G-quadruplex-binding protein.

Authors: González, Verónica; Guo, Kexiao; Hurley, Laurence; Sun, Daekyu

Published In J Biol Chem, (2009 Aug 28)

Abstract: myc is a proto-oncogene that plays an important role in the promotion of cellular growth and proliferation. Understanding the regulation of c-myc is important in cancer biology, as it is overexpressed in a wide variety of human cancers, including most gynecological, breast, and colon cancers. We previously demonstrated that a guanine-rich region upstream of the P1 promoter of c-myc that controls 85-90% of the transcriptional activation of this gene can form an intramolecular G-quadruplex (G4) that functions as a transcriptional repressor element. In this study, we used an affinity column to purify proteins that selectively bind to the human c-myc G-quadruplex. We found that nucleolin, a multifunctional phosphoprotein, binds in vitro to the c-myc G-quadruplex structure with high affinity and selectivity when compared with other known quadruplex structures. In addition, we demonstrate that upon binding, nucleolin facilitates the formation and increases the stability of the c-myc G-quadruplex structure. Furthermore, we provide evidence that nucleolin overexpression reduces the activity of a c-myc promoter in plasmid presumably by inducing and stabilizing the formation of the c-myc G-quadruplex. Finally, we show that nucleolin binds to the c-myc promoter in HeLa cells, which indicates that this interaction occurs in vivo. In summary, nucleolin may induce c-myc G4 formation in vivo.

PubMed ID: 19581307 Exiting the NIEHS site

MeSH Terms: Base Sequence; G-Quadruplexes*; HeLa Cells; Humans; Molecular Sequence Data; Phosphoproteins/chemistry; Phosphoproteins/genetics; Phosphoproteins/metabolism*; Promoter Regions, Genetic; Protein Binding; Proto-Oncogene Proteins c-myc/chemistry*; Proto-Oncogene Proteins c-myc/genetics*; Proto-Oncogene Proteins c-myc/metabolism; RNA-Binding Proteins/chemistry; RNA-Binding Proteins/genetics; RNA-Binding Proteins/metabolism*

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